Research ArticlesAnnexin A10 and HES-1 Immunohistochemistry in Right-sided Traditional Serrated Adenomas Suggests an Origin From Sessile Serrated AdenomaNourbakhsh, Mahra MD, PhD; Minoo, Parham MD, PhDAuthor Information Department of Pathology and Laboratory Medicine, University of Calgary, Cumming School of Medicine and Calgary Laboratory Services, Calgary, AB, Canada Supported by a research fund from the Calgary Laboratory Services (RS17-600) received by Parham Minoo. The authors declare no conflict of interest. Reprints: Parham Minoo, MD, PhD, Department of Pathology, University of Calgary and Calgary Laboratory Services, Foothills Medical Centre, McCaig Tower, Room 7563, 1403-29th Street NW, Calgary, AB, Canada T2N 2T9 (e-mail: [email protected]). Applied Immunohistochemistry & Molecular Morphology: April 2020 - Volume 28 - Issue 4 - p 296-302 doi: 10.1097/PAI.0000000000000740 Buy Metrics Abstract There is increasing body of evidence to suggest that some colonic serrated polyps do not fit morphologically with any of the proposed categories for serrated polyps recommended by the World Health Organization. Most of these polyps have morphologic features of traditional serrated adenoma (TSA) admixed with areas resembling sessile serrated adenoma (SSA) or hyperplastic polyp (HP). Based on these findings it has been suggested that at least some TSAs may arise in association with precursor HP or SSA lesions, particularly those that develop in right colon. To further evaluate this hypothesis, 39 serrated polyps from right side of the colon (cecum, ascending, and transverse colon) with mixed features of TSA and SSA were evaluated by 2 immunostains previously shown to represent markers of SSA. One is Annexin A10 which shows upregulated expression in SSA and the other is Hes-1 which is shown to be down regulated in SSA. The expression patterns of these markers were evaluated in SSA and TSA components of hybrid polyps and compared with control groups (pure SSAs and TSAs of right colon). SSA component in hybrid polyps did not show any significant difference in staining pattern compared with that seen in TSA component of hybrid polyps or in pure TSA polyps. These findings further support the hypothesis that recognizes SSA as a precursor lesion for TSA in the right colon. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.